That's not the advice you gave. In fact you gave no advice, you simply proclaimed your superiority when it comes to past decision making, in that you only worked for companies that make money.

Your reply was intentionally snarky at best; obnoxiously insulting, demeaning and entirely non-useful at worst.

You should have stated it this way in your original comment. Instead your comment comes a across as snarky and unhelpful.

Would you also recommend that he eat food for sustenance, and continue metabolizing it with oxygen?

I agree. But also to counter the optimism would be to clearly explain that if a company does not have a solid fundamental plan to make money that is not 'running ads' or 'when we have millions of users it will come to us', you might not want to work there. There are plenty of great startups that have a solid plan and yes, it is more risk than working for Microsoft, however, it is not as much risk as working for a company that needs investment rounds until they figure out how to actually make money. I find those the most frightening and many of those you can find here. That is not to say even those do not stand a chance, but it is a big risk.